According to the Center for Public Integrity, at least 16 million Americans are in the potential path of toxic acid fumes if an industrial incident were to occur. It was news to the neighbors of Husky Energy in Superior, Wisconsin, that they belong to that crowd.
The hazardous material involved in this case is hydrofluoric acid or HF. The residents of Superior learned that they belonged to the 16 million in the path of a potential HF release when an explosion shook the neighboring refinery in late April. As a precaution, everyone in a 3-mile radius and up to 10 miles downwind was evacuated. Citizens later learned that the extensive evacuation related to the risk that the HF tank would be compromised due to the explosions and ongoing fire.
Getting the concentrated liquid HF acid over a patch of skin the size of a man's palm has been sufficient exposure to be fatal without treatment (an effective treatment is available). What makes it also particularly hazardous is that it does not just 'spill' but easily aerosolizes and moves offsite in a cloud. It is used in refineries as a catalyst to alkylate hydrocarbons, which are then blended into high octane gas. While HF is used safely in many applications most of the time, there are safer substitutes available for this alkylation process.
The Chemical Safety and Hazard Investigation Board has a team at the site and we cannot know exactly what caused the terrible incident until their work is complete, but it can be said in general that everything turned out as well as an emergency manager could possibly hope in the face of such a significant incident.
There were no fatalities, and only one employee was injured severely enough to require extended hospitalization; he is reported to be in "good condition" after suffering blast injuries. The safety measures to protect the HF tank in case of nearby fires worked, and no HF was released. All of this may be luck, but more likely it reflects that the safety measures in place even for unintended events functioned as required.
On the other hand, shrapnel from the primary explosions pierced an asphalt tank, releasing a flow of the flammable material to feed the fire. Safety measures such as large berms (dike walls) around each tank prevented the liquid from spreading the fire, but extinguishing such a fire took time and a lot of firefighting foam (another potential chemical hazard, although the worst foams have been banned now.)
So even with a lot of things that appear to have gone right, this still turned into a major incident and disrupted a lot of lives. That is ultimately the reason why refineries need to evaluate their use of HF: even with our best safety management technologies, sometimes things go wrong.
There are safer alternatives, including use of other acids less likely to travel through the air in case of an incident. Or there are refineries now using a completely new technology, solid acid catalysts, that are a much safer substitute. When it is possible to avoid the worst risks altogether and still get the benefits of chemistry in our lives, that is the path that must be preferred.
In the wake of the evacuation, the mayors of Superior and its twin port, Duluth Minnesota, have recognized the economic value that the refinery jobs bring to the community but are pressing the Husky Energy refinery to find a safer alternative to the HF. Husky Energy has promised to conduct a renewed review of the HF process safety as they rebuild.
The incident is also renewing pressures on the Trump administration which has delayed an Obama-era amendment to the risk management program (RMP) rules that would require facilities handling hazardous substances to document a review of safer alternatives in their RMP reports.
In Europe, the law requires industrial sites handling these types of chemicals to inform neighbors about the hazards, the measures taken to minimize risks and the recommended emergency procedures in case of a serious incident - without the public having to ask for this information. It is too bad that Americans have to go to great lengths to learn the same information.
You can check your street address at the EPA's Vulnerable Zone Indicator System webpage. They will email you if the address about which you are inquiring is in an area that could be affected by a Risk Management Plan which businesses that handle hazardous chemicals are required to file with the EPA.
Being informed about emergency plans in advance can help citizen prepare and improve outcomes in case of an incident. It can also give citizens power to get involved with industry in their community. Dialogue and a sense of responsibility to the neighbors can be strong tools to push towards the best balance of economic benefits with the lowest technically and economically feasible risk.